> `WaitGroup`的用途是使得主協程一直阻塞等待直到所有相關的子協程都已經完成了任務后再繼續運行 ~~~ package main import ( "fmt" "sync" "time" ) func process(i int, wg *sync.WaitGroup) { fmt.Printf("Goroutine %d started\n", i) time.Sleep(2 * time.Second) fmt.Printf("Goroutine %d ended\n", i) wg.Done() } func main() { var wg sync.WaitGroup for i := 0; i < 3; i++ { wg.Add(1) go process(i, &wg) } wg.Wait() fmt.Println("All go routines finished executing") } ~~~ > 將其改為匿名函數方式 ~~~ package main import ( "fmt" "sync" "time" ) func main() { var wg sync.WaitGroup for i := 0; i < 3; i++ { wg.Add(1) go func(num int) { fmt.Printf("Goroutine %d started\n", num) time.Sleep(2 * time.Second) fmt.Printf("Goroutine %d ended\n", num) wg.Done() }(i) } wg.Wait() fmt.Println("All go routines finished executing") } ~~~